Battery cell and terminal device

Abstract

The invention discloses a battery cell and a terminal device. The battery cell comprises an electrode assembly and a packaging bag. At least one corner of the electrode assembly is provided with a first arc, and the radius of the first arc is R1 when observed in the first direction. The packaging bag comprises a main body part, and the electrode assembly is arranged in the main body part. A second arc is arranged at the corner, adjacent to the first arc, of the body part, and the second arc and the first arc are arranged at intervals. The radius of the second arc is R2 when observed in the first direction, and R2 is smaller than R1. The first direction is the thickness direction of the battery cell. The second circular arc and the first circular arc are arranged at intervals, R2 is smaller than R1, so that the first circular arc is passivated compared with the second circular arc, and a buffer space is formed between the second circular arc and the first circular arc. When the electrode assembly expands in the circulation process, the buffer space can reduce the risk of contact and interference of the first arc and the second arc, so that the risk of deformation or damage of the battery cell caused by the fact that the packaging bag extrudes the angular position of the electrode assembly is reduced, and the safety performance of the battery cell is improved.

Description

Battery cells and terminal devices Technical Field

[0001] This application relates to the field of energy storage technology, and in particular to a battery cell and terminal device. Background Technology

[0002] Existing battery cell packaging bags are typically made of flexible film. The gaps between the corners of the packaging bag and the corners of the electrode assembly are small. During cycling, the electrode assembly expands, causing the packaging bag to squeeze the corners of the electrode assembly, which can lead to deformation or damage to the battery cell, affecting its safety performance. Summary of the Invention

[0003] In view of the above, this application provides a battery cell that can improve safety performance.

[0004] An embodiment of this application provides a battery cell, which includes an electrode assembly and a packaging bag. At least one corner of the electrode assembly is provided with a first arc, the radius of which is R1 when viewed along a first direction. The packaging bag includes a main body, within which the electrode assembly is disposed. A second arc is provided at a corner of the main body adjacent to the first arc, the second arc being spaced apart from the first arc. The radius of the second arc is R2, where R2 < R1, when viewed along the first direction. The first direction is the thickness direction of the battery cell.

[0005] In the aforementioned battery cell, the second arc is spaced apart from the first arc, with R2 < R1, so that the first arc is blunted compared to the second arc, which helps to form a buffer space between the second and first arcs. When the electrode assembly expands during cycling, the buffer space can reduce the risk of the first and second arcs coming into contact and interfering, thereby reducing the risk of the battery cell deforming or breaking due to the corner of the electrode assembly being squeezed by the packaging bag, and improving the safety performance of the battery cell.

[0006] In some embodiments of this application, 1mm≤R2≤3mm is used to improve the structural strength of the packaging bag, facilitate the processing of the packaging bag, and help improve the energy density of the battery cell.

[0007] In some embodiments of this application, the electrode assembly includes a negative electrode, a positive electrode, and a separator. The negative and positive electrode are alternately arranged along a first direction, and the separator is disposed between the negative and positive electrode. Along the first direction, the projection of the positive electrode lies within the projection of the negative electrode to reduce the risk of lithium plating at the edge of the negative electrode. A first arc is disposed on the negative electrode.

[0008] In some embodiments of this application, a third arc is provided at the corner of the positive electrode adjacent to the first arc. Viewed along the first direction, the radius of the third arc is R3, where R2 < R3 < R1. (The last part, "R2 < R3 < R1," is a partial translation of the original text and doesn't need a direct translation.) 3，This allows the third arc to be positioned on the side of the first arc away from the second arc, reducing the risk of the third arc extending into the buffer space. This is achieved by R3 < R 1， This helps to increase the overlap area of ​​the negative and positive electrodes at the corners of the electrode assembly, which in turn helps to improve the energy density of the battery cell.

[0009] In some embodiments of this application, viewed along a first direction, the electrode assembly includes two first side surfaces disposed opposite each other along a second direction, and two second side surfaces disposed opposite each other along a third direction. The first side surfaces and the second side surfaces are connected by a first arc. The first direction, the second direction, and the third direction are perpendicular to each other. Viewed along the first direction, the main body includes two first walls disposed opposite each other along the second direction, and two second walls disposed opposite each other along the third direction. The first walls and the second walls are connected by a second arc. The first walls and their corresponding first side surfaces are arranged along the second direction, and the second walls and their corresponding second side surfaces are arranged along the third direction. Optionally, the first walls and their corresponding first side surfaces are spaced apart or abutted together along the second direction, and the second walls and their corresponding second side surfaces are spaced apart or abutted together along the third direction.

[0010] In some embodiments of this application, when viewed along a first direction, the center of the first arc is located on the electrode assembly, and the center of the second arc is located on the side of the main body facing the electrode assembly, so that the first arc and the second arc are respectively convex arcs.

[0011] In some embodiments of this application, the angle between the line connecting the first arc and its center is 90°, and the angle between the line connecting the second arc and its center is also 90°. Along the second direction, the distance between the first wall and the corresponding first side surface is d1, and along the third direction, the distance between the two second side surfaces is L. R1, R2, d1, and L satisfy the following relationship: R2 2 <R1 2 <L×d1 / (4-π) to improve the energy density of the battery cell.

[0012] In some embodiments of this application, when viewed along a first direction, the center of the first arc is located outside the electrode assembly, and the center of the second arc is located on the side of the main body away from the electrode assembly, so that the first arc and the second arc are concave arcs respectively.

[0013] In some embodiments of this application, the angle between the line connecting the first arc and its center is 90°, and the angle between the line connecting the second arc and its center is also 90°. Along the second direction, the distance between the first wall and the corresponding first side surface is d1, and along the third direction, the distance between the two second side surfaces is L. R1, R2, d1, and L satisfy the following relationship: R2 2 <R1 2 <L×d1 / π) to increase the energy density of the battery cell.

[0014] In some embodiments of this application, the electrode assembly is a stacked structure or a wound structure.

[0015] In some embodiments of this application, the thickness of the battery cell along the first direction is H, where H ≤ 3.5 mm, to meet the size requirements of ultra-thin battery cells. Typically, ultra-thin battery cells have fewer electrode layers, making them more prone to deformation or breakage. By setting a second arc spaced apart from the first arc, with R2 < R1, the risk of deformation or breakage of the ultra-thin battery cell caused by the packaging bag squeezing the corners of the electrode assembly is reduced, thus improving the safety performance of the ultra-thin battery cell.

[0016] Embodiments of this application also provide a terminal device, which includes the battery cell described in the above embodiments.

[0017] In the aforementioned battery cell and terminal device, the second arc is spaced apart from the first arc, with R2 < R1, so that the first arc is blunted compared to the second arc, which helps to form a buffer space between the second arc and the first arc. When the electrode assembly expands during cycling, the buffer space can reduce the risk of the first arc and the second arc coming into contact and interfering, thereby reducing the risk of the battery cell deforming or breaking due to the corner of the electrode assembly being squeezed by the packaging bag, and improving the safety performance of the battery cell. Attached Figure Description

[0018] Figure 1 is a schematic diagram of the first structure of the battery cell in one embodiment of this application.

[0019] Figure 2 is a schematic diagram of the electrode assembly of the battery cell in one embodiment of this application.

[0020] Figure 3 is a schematic diagram of the second structure of the battery cell in one embodiment of this application.

[0021] Figure 4 is a schematic diagram of the dimensions of the battery cell in one embodiment of this application.

[0022] Figure 5 is a schematic diagram of the electrode assembly of the battery cell in another embodiment of this application.

[0023] Figure 6 is a schematic diagram of the unfolded structure of the positive electrode and the negative electrode in another embodiment of this application.

[0024] Figure 7 is a schematic diagram of the battery cell structure in another embodiment of this application.

[0025] Figure 8 is a schematic diagram of the electrode assembly of the battery cell in another embodiment of this application.

[0026] Figure 9 is a schematic diagram of the structure of a terminal device in one embodiment of this application.

[0027] Explanation of main component symbols

[0028] Battery cells 100A, 100B, 100C, 100D

[0029] Terminal device 200

[0030] Electrode assembly 10

[0031] 10A negative electrode

[0032] Positive electrode 10B

[0033] Diaphragm 10C

[0034] First arc 11

[0035] Third arc 12

[0036] First side view 13

[0037] Second side 14

[0038] Packaging bag 20

[0039] Main body 30

[0040] Buffer space 30A

[0041] Second arc 31

[0042] First Wall 32

[0043] Second Wall 33

[0044] Packaging section 40

[0045] Corner sealing 41

[0046] Top edge sealing 42

[0047] Side sealing 43

[0048] JE50

[0049] First direction Z

[0050] Second direction Y

[0051] Third direction X

[0052] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this application. Detailed Implementation

[0053] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0054] It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or may also have a component that is centrally located. When a component is considered to be "set" on another component, it can be directly set on the other component or may also have a component that is centrally located.

[0055] When one value is considered "equal" to another, it means that they are equal within a set deviation range, which is within 5%. In other words, if at least one of the two values ​​fluctuates within the set deviation range, they are considered approximately equal even if their values ​​are not equal. Similarly, when one value is considered to have a "1:1" ratio with another, it means that they are equal within a set deviation range, which is within 5%. Again, if at least one of the two values ​​fluctuates within the set deviation range, they are considered equal in ratio even if their values ​​are not equal.

[0056] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. The term "overlap" as used herein refers to the overlapping of the projected portions of two components or the coincidence of the projected portions of two components.

[0057] An embodiment of this application provides a battery cell, which includes an electrode assembly and a packaging bag. At least one corner of the electrode assembly is provided with a first arc, the radius of which is R1 when viewed along a first direction. The packaging bag includes a main body, within which the electrode assembly is disposed. A second arc is provided at a corner of the main body adjacent to the first arc, the second arc being spaced apart from the first arc. The radius of the second arc is R2, where R2 < R1, when viewed along the first direction. The first direction is the thickness direction of the battery cell.

[0058] In the aforementioned battery cell, the second arc is spaced apart from the first arc, with R2 < R1, so that the first arc is blunted compared to the second arc, which helps to form a buffer space between the second and first arcs. When the electrode assembly expands during cycling, the buffer space can reduce the risk of the first and second arcs coming into contact and interfering, thereby reducing the risk of the battery cell deforming or breaking due to the corner of the electrode assembly being squeezed by the packaging bag, and improving the safety performance of the battery cell.

[0059] The embodiments of this application will be further described below with reference to the accompanying drawings.

[0060] Example 1

[0061] Please refer to Figures 1 and 2 together. One embodiment of this application provides a battery cell 100A, which is used in a secondary battery. A secondary battery is a battery that can be used again after being discharged by recharging to activate the active materials.

[0062] The battery cell 100A includes an electrode assembly 10 and a packaging bag 20. The electrode assembly 10 includes a negative electrode 10A, a positive electrode 10B, and a separator 10C. The negative electrode 10A and the positive electrode 10B are alternately arranged along a first direction Z, and the separator 10C is disposed between the negative electrode 10A and the positive electrode 10B. The first direction Z is the thickness direction of the battery cell 100. The electrode assembly 10 is used to convert chemical energy into electrical energy.

[0063] The packaging bag 20 includes a main body 30, which is formed by sealing multiple side walls. The electrode assembly 10 and electrolyte are disposed inside the main body 30.

[0064] At least one corner of the electrode assembly 10 is provided with a first arc 11, the radius of which is R1 when viewed along the first direction Z. A second arc 31 is provided at the corner of the main body 30 adjacent to the first arc 11, the second arc 31 being spaced apart from the first arc 11. The radius of the second arc 31 is R2 when viewed along the first direction Z, where R2 < R1, so that the first arc 11 is blunted compared to the second arc 31, which facilitates the formation of a buffer space 30A between the second arc 31 and the first arc 11. When the electrode assembly 10 expands during cycling, the buffer space 30A can reduce the risk of the first arc 11 and the second arc 31 contacting and interfering, thereby reducing the risk of deformation or damage to the battery cell 100A caused by the packaging bag 20 squeezing the corner of the electrode assembly 10, and improving the safety performance of the battery cell 100A.

[0065] It should be noted that the measurement methods for R1 and R2 are as follows: A cross-sectional view of the 100A battery cell is obtained along the first direction Z using CT (computed tomography). After obtaining the first arc profile of the first arc 11, arbitrarily select two points on the first arc profile to draw tangents. Then, draw a perpendicular line from the tangent points to the tangents. The two perpendicular lines intersect at a single point, which is the center of the first arc 11. The distance from any point on the first arc profile to the center of the first arc 11 is then measured; this is R1. Similarly, after obtaining the second arc profile of the second arc 31, arbitrarily select two points on the second arc profile to draw tangents. Then, draw a perpendicular line from the tangent points to the tangents. The two perpendicular lines intersect at a single point, which is the center of the second arc 31. The distance from any point on the second arc profile to the center of the second arc 31 is then measured; this is R2.

[0066] In some embodiments, the electrode assembly 10 is a stacked structure, with the negative electrode 10A, the separator 10C and the positive electrode 10B stacked along the first direction Z.

[0067] Please refer to Figures 1 and 2. In some embodiments, 1mm ≤ R2 ≤ 3mm. When R2 is too small (less than 1mm), stress concentration easily occurs in the second arc 31, affecting the structural strength of the packaging bag 20 and hindering its processing. When R2 is too large (greater than 3mm), the corners of the packaging bag 20 tend to occupy a large amount of space, resulting in wasted space and affecting the energy density of the battery cell 100A. By limiting R2 to 3mm, the structural strength of the packaging bag 20 is improved, facilitating its processing and increasing the energy density of the battery cell 100A.

[0068] Optionally, R2 can be any value within the range of 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, 2mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm, 2.5mm, 2.6mm, 2.7mm, 2.8mm, 2.9mm, 3mm, or any other value within the range of 1mm≤R2≤3mm.

[0069] Please continue referring to Figures 1 and 2. In some embodiments, along the first direction Z, the projection of the positive electrode 10B is located within the projection of the negative electrode 10A to reduce the risk of lithium plating at the edge of the negative electrode 10A. A first arc 11 is disposed on the negative electrode 10A.

[0070] In some embodiments, a third arc 12 is provided at the corner of the positive electrode 10B adjacent to the first arc 11. Viewed along the first direction Z, the radius of the third arc 12 is R3, where R2 < R3 < R1. (The last part, "R2 < R1," is a partial translation of the original text and doesn't need a direct translation.) 3， This is to ensure that the third arc 12 is located on the side of the first arc 11 away from the second arc 31, reducing the risk of the third arc 12 extending into the buffer space 30A. This is achieved by R3 < R 1， This is beneficial to increasing the overlap area of ​​the negative electrode 10A and the positive electrode 10B at the corner of the electrode assembly 10, which in turn helps to improve the energy density of the battery cell 100A.

[0071] In some embodiments, along the first direction Z, the projection of the diaphragm 10C coincides with the projection of the negative electrode 10A.

[0072] It is understood that in some embodiments, the separator 10C is made of a flexible material, and the edge of the separator 10C extends beyond the edge of the negative electrode 10A to improve the stability of the isolation between the negative electrode 10A and the positive electrode 10B, without affecting the buffer space 30A. Optionally, the separator 10C is bent beyond the edge of the negative electrode 10A.

[0073] Referring to Figures 1 and 2, in some embodiments, viewed along the first direction Z, the electrode assembly 10 includes two first side surfaces 13 disposed opposite each other along the second direction Y, and two second side surfaces 14 disposed opposite each other along the third direction X. The first side surfaces 13 and the second side surfaces 14 are connected by a first arc 11. Specifically, viewed along the first direction Z, the projections of the first side surfaces 13 and the second side surfaces 14 are connected by the projection of the first arc 11. The first direction Z, the second direction Y, and the third direction X are perpendicular to each other.

[0074] It should be noted that the two first side surfaces 13 and the two second side surfaces 14 are respectively disposed on the negative electrode 10A.

[0075] Optionally, when viewed along the first direction Z, the cell 100A forms a shape similar to a rectangle, wherein the second direction Y is the length direction of the cell 100A, and the third direction X is the width direction of the cell 100A.

[0076] Viewed along the first direction Z, the main body 30 includes two first walls 32 arranged opposite each other along the second direction Y, and two second walls 33 arranged opposite each other along the third direction X. The first walls 32 and the second walls 33 are connected by a second arc 31. Specifically, viewed along the first direction Z, the projections of the first walls 32 and the second walls 33 are connected by the projection of the second arc 31. The first walls 32 and their corresponding first side surfaces 13 are arranged along the second direction Y, and the second walls 33 and their corresponding second side surfaces 14 are arranged along the third direction X.

[0077] Specifically, taking one of the first walls 32 as an example, along the second direction Y, the one of the two first side faces 13 that is closer to the first wall 32 is the corresponding first side face 13. Taking one of the second walls 33 as an example, along the third direction X, the one of the two second side faces 14 that is closer to the second wall 33 is the corresponding second side face 14.

[0078] In some embodiments, the first wall 32 and the corresponding first side 13 are spaced apart along the second direction Y to reduce the risk of deformation or damage to the battery cell 100A caused by the packaging bag 20 squeezing the electrode assembly 10 in the second direction Y, thereby improving the safety performance of the battery cell 100A.

[0079] In some embodiments, the second wall 33 and the corresponding second side 14 are spaced apart along the third direction X to reduce the risk of deformation or damage to the battery cell 100A caused by the packaging bag 20 squeezing the electrode assembly 10 in the third direction X, thereby improving the safety performance of the battery cell 100A.

[0080] Please refer to Figure 3. In some embodiments, the first wall 32 and the corresponding first side 13 are abutted along the second direction Y to improve the space utilization of the electrode assembly 10 in the main body 30 along the second direction Y, which is beneficial to improving the energy density of the battery cell 100A.

[0081] In some embodiments, the second wall 33 and the corresponding second side 14 are abutted along the third direction X to improve the space utilization of the electrode assembly 10 in the main body 30 along the third direction X, which is beneficial to improving the energy density of the battery cell 100A.

[0082] Referring to Figure 4, in some embodiments, when viewed along the first direction Z, the two first side surfaces 13 and the two second side surfaces 14 form a rectangular shape, and the two first walls 32 and the two second walls 33 form a rectangular shape. Correspondingly, the electrode assembly 10 and the main body 30 each have four corner positions.

[0083] Optionally, the electrode assembly 10 has a first arc 11 at each of its four corners, and the main body 30 has a second arc 31 and a buffer space 30A at each of its four corners. When the electrode assembly 10 expands during cycling, the four buffer spaces 30A can further reduce the risk of the battery cell 100A being deformed or damaged due to the packaging bag 20 squeezing the corners of the electrode assembly 10, thereby improving the safety performance of the battery cell 100A.

[0084] Please continue to refer to Figure 4. In some embodiments, when viewed along the first direction Z, the center O1 of the first arc 11 is located on the electrode assembly 10, and the center O2 of the second arc 31 is located on the side of the main body 30 facing the electrode assembly 10, so that the first arc 11 and the second arc 31 are respectively convex arcs.

[0085] In some embodiments, when viewed along the first direction Z, the third arc 12 is an outwardly convex arc to increase the overlap area of ​​the negative electrode 10A and the positive electrode 10B at the corner of the electrode assembly 10, which is beneficial to improving the energy density of the cell 100A.

[0086] In some embodiments, the electrode assembly 10 is provided with a first arc 11 at each of its four corners, and the main body 30 is provided with a second arc 31 and a buffer space 30A at each of its four corners. The angle between the line connecting the first arc 11 and its center O1 is α, where α = 90°, and the angle between the line connecting the second arc 31 and its center O2 is β, where β = 90°.

[0087] Along the second direction Y, the distance between the first wall 32 and the corresponding first side 13 is d1, and along the third direction X, the distance between the two second side 14 is L. R1, R2, d1, and L satisfy the following relationship: R2 2 <R1 2 <L×d1 / (4-π) to increase the energy density of the battery cell to 100A.

[0088] The detailed derivation process is as follows:

[0089] Along the second direction Y, the distance between the two first side surfaces 13 is W.

[0090] The area of ​​a single layer of electrode assembly 10 is L×W. The area lost by each first arc 11 is R1. 2 -1 / 4πR1 2 The area lost by the four first arcs 11 is 4 × (R1) 2 -1 / 4πR1 2 ), which simplifies to 4R1 2 -πR1 2 A set of first side faces 13 and corresponding first side faces 13 are spaced apart, with the area of ​​the loss being L×d1.

[0091] The loss ratio for the first energy density is (4R1) 2 -πR1 2 The loss ratio for the second energy density is (L×d1) / L×W.

[0092] As the size of the 100A cell changes, the loss ratio of the first energy density and the loss ratio of the second energy density will change. When the loss ratio of the first energy density is less than the loss ratio of the second energy density, the first arc 11 will have a greater benefit in increasing the energy density of the 100A cell. Correspondingly, (4R1) 2 -πR1 2 ) / L×W<(L×d1) / L×W. Simplifying, we get R1. 2 <L×d1 / (4-π).

[0093] Since R2 < R1, we can further obtain R2 2 <R1 2 <L×d1 / (4-π).

[0094] Please continue referring to Figure 1. In some embodiments, the battery cell 100A further includes two tabs 50 with different polarities. One tab 50 is connected to the negative electrode 10A, and the other tab 50 is connected to the positive electrode 10B. The tabs 50 extend out of the packaging bag 20 along the second direction Y to facilitate connection with external circuitry. Viewed along the first direction Z, the tabs 50 extend from one of the first walls 32 and are spaced apart from the second arc 31 to reduce the risk of interference between the tabs 50 and the corners of the packaging bag 20, which could affect the structural strength of the corners of the packaging bag 20.

[0095] Optionally, the tab 50 and the negative electrode 10A are integrally formed, or the tab 50 is welded to the negative electrode 10A. The tab 50 and the positive electrode 10B are integrally formed, or the tab 50 is welded to the positive electrode 10B.

[0096] Please refer to Figure 1. In some embodiments, the packaging bag 20 further includes a sealing portion 40 for sealing the main body 30. The sealing portion 40 includes a corner seal 41, a top seal 42, and a side seal 43. The corner seal 41 is connected to a second arc 31, the top seal 42 is connected to a first wall 32 with tabs 50 extending from the top seal 42, and the side seal 43 is connected to a second wall 33. The top seal 42 and the side seal 43 are connected by the corner seal 41 to improve the sealing performance of the main body 30.

[0097] In some embodiments, the thickness of the battery cell 100A along the first direction Z is H, where H ≤ 3.5 mm, to meet the size requirements of ultra-thin battery cells. Ultra-thin battery cells typically have fewer electrode layers, making them more prone to deformation or breakage. By using a second arc 31 spaced apart from the first arc 11, with R2 < R1, the risk of deformation or breakage of the ultra-thin battery cell caused by the packaging bag 20 squeezing the corner of the electrode assembly 10 is reduced, thus improving the safety performance of the ultra-thin battery cell.

[0098] Example 2

[0099] Please refer to Figures 5 and 6 together. One embodiment of this application also provides a battery cell 100B. The difference between battery cell 100B and battery cell 100A is that the electrode assembly 10 has a wound structure, with the negative electrode 10A, separator 10C and positive electrode 10B wound together.

[0100] During the preparation process, the unfolded negative electrode 10A and positive electrode 10B are die-cut or laser-cut to form a straight section and an arc-shaped section on the side of the negative electrode 10A in the second direction Y, and a straight section and an arc-shaped section on the side of the positive electrode 10B in the second direction Y. Then, the negative electrode 10A, the separator 10C and the positive electrode 10B are stacked and wound. The straight sections of the negative electrode 10A overlap to form a first side surface 13, and the arc-shaped sections of the negative electrode overlap to form a first arc 11. The straight sections of the positive electrode 10B overlap but do not exceed the first side surface 13, and the arc-shaped sections of the positive electrode 10B overlap to form a third arc 12.

[0101] Apart from the differences mentioned above, the parameters of cell 100B and cell 100A are roughly the same, and you can refer to the description of cell 100A above.

[0102] Example 3

[0103] Please refer to Figure 7. One embodiment of this application also provides a battery cell 100C. The difference between battery cell 100C and battery cell 100A is that the first arc 11, the second arc 31, and the third arc 12 are all concave arcs.

[0104] When viewed along the first direction Z, the center O1 of the first arc 11 is located outside the electrode assembly 10, and the center O2 of the second arc 31 is located on the side of the main body 30 away from the electrode assembly 10, so that the first arc 11 and the second arc 31 are concave arcs respectively.

[0105] In some embodiments, when viewed along the first direction Z, the third arc 12 is concave to reduce the risk of the third arc 12 extending into the buffer space 30A.

[0106] In some embodiments, the electrode assembly 10 is provided with a first arc 11 at each of its four corners, and the main body 30 is provided with a second arc 31 and a buffer space 30A at each of its four corners. The angle between the line connecting the first arc 11 and its center O1 is α, where α = 90°, and the angle between the line connecting the second arc 31 and its center O2 is β, where β = 90°.

[0107] Along the second direction Y, the distance between the first wall 32 and the corresponding first side 13 is d1, and along the third direction X, the distance between the two second side 14 is L. R1, R2, d1, and L satisfy the following relationship: R2 2 <R1 2 <L×d1 / π, to increase the energy density of the battery cell to 100C.

[0108] The detailed derivation process is as follows:

[0109] Along the second direction Y, the distance between the two first side surfaces 13 is W.

[0110] The area of ​​a single layer of electrode assembly 10 is L×W. The area lost by each first arc 11 is R1. 2 -1 / 4πR1 2 The area lost by the four first arcs 11 is 4 × (1 / 4πR1) 2 ), which simplifies to πR1 2 A set of first side faces 13 and corresponding first side faces 13 are spaced apart, with the area of ​​the loss being L×d1.

[0111] The loss ratio for the first energy density is πR1 2 / L×W. The loss ratio for the second energy density is (L×d1) / L×W.

[0112] As the size of the 100A cell changes, the loss ratio of the first energy density and the loss ratio of the second energy density will change. When the loss ratio of the first energy density is less than the loss ratio of the second energy density, the first arc 11 will have a greater benefit in increasing the energy density of the 100C cell. Correspondingly, πR1 2 / L×W<(L×d1) / L×W. Simplifying, we get R1.2 <L×d1 / π.

[0113] Since R2 < R1, we can further obtain R2 2 <R1 2 <L×d1 / π.

[0114] Apart from the differences mentioned above, the parameters of cell 100C and cell 100A are roughly the same. Please refer to the description of cell 100A above.

[0115] Example 4

[0116] Please refer to Figure 8. An embodiment of this application also provides a battery cell 100D. The difference between battery cell 100D and battery cell 100C is that the electrode assembly 10 has a wound structure, with the negative electrode 10A, separator 10C and positive electrode 10B wound together.

[0117] Apart from the differences mentioned above, the parameters of cell 100D and cell 100C are roughly the same. Please refer to the description of cell 100C above.

[0118] Please continue to refer to Figure 9. An embodiment of this application also provides a terminal device 200, which includes the battery cells (100A, 100B, 100C, 100D) in any of the above embodiments.

[0119] Optionally, the terminal device 200 may be a vehicle, mobile phone, portable device, laptop computer, ship, spacecraft, electric toy, and power tool, etc.

[0120] In the aforementioned battery cells (100A, 100B, 100C, 100D) and terminal device 200, at least one corner of the electrode assembly 10 is provided with a first arc 11, the radius of which is R1. A second arc 31 is provided at a corner of the main body 30 adjacent to the first arc 11, and the second arc 31 is spaced apart from the first arc 11. The radius of the second arc 31 is R2, where R2 < R1, so that the first arc 11 is blunted compared to the second arc 31, which facilitates the formation of a buffer space 30A between the second arc 31 and the first arc 11. When the electrode assembly 10 expands during cycling, the buffer space 30A can reduce the risk of the first arc 11 and the second arc 31 contacting and interfering, thereby reducing the risk of the battery cells (100A, 100B, 100C, 100D) being deformed or damaged due to the corner of the electrode assembly 10 being squeezed by the packaging bag 20, and improving the safety performance of the battery cells (100A, 100B, 100C, 100D).

[0121] The following describes the specific implementation methods of the battery cells in the embodiments and comparative examples.

[0122] 1. Deformation test of the cell head:

[0123] Measuring the first expansion ratio K1 of the battery cell: Select three measurement points on the cell head (the part where the cell extends beyond the tabs is called the battery head), with these three points located between the two tabs. Before the cell begins cycling, measure the thickness at each of the three measurement points using a micrometer, and take the average of the three thicknesses as the initial thickness T0 of the cell head. After 140 cycles, measure the thickness at each of the three measurement points using a micrometer, and take the average of the three thicknesses as the post-cycle thickness T1 of the cell head. The first expansion ratio K1 is calculated using the following formula: K1 = (T1 - T0) / T0 × 100%.

[0124] The second expansion ratio K2 of the battery cell is measured using a PPG (Parallel Plate Gauge) before the cell begins cycling. Specifically, the secondary battery is placed between two plates, and a pressure of 700g is applied. The distance between the two plates is taken as the initial thickness T2 of the entire cell. After 140 cycles, the thickness T3 of the entire cell after cycling is measured using a PPG. The second expansion ratio K2 is calculated using the following formula: K2 = (T3 - T2) / T2 × 100%.

[0125] The deformation P of the cell head is calculated using the following formula: P = K1 - K2. When P = 0, it indicates that no deformation has occurred at the cell head. The larger P is, the greater the deformation of the cell head.

[0126] 2. Cell energy density test:

[0127] The cell energy density testing method involves dividing the energy value by the cell volume. The energy value is the product of the cell capacity and voltage. The cell volume is the product of the cell's initial length, width, and thickness—that is, the product of the cell's length, width, and thickness before cycling—to reduce errors caused by thickness changes after cycling. The energy density obtained through this testing method is the cell's initial energy density.

[0128] Example 1:

[0129] A type of battery cell 100, with an initial thickness of 1.4mm, a length of 110mm, and a width of 50mm at 50% SOC, is assembled as follows:

[0130] (1) Preparation of negative electrode sheet: The negative electrode active materials artificial graphite, conductive carbon black (Super P), and styrene-butadiene rubber (SBR) are mixed in a weight ratio of 96:1.5:2.5, and deionized water is added as a solvent to prepare a slurry with a weight percentage of 50 wt%. The slurry is stirred evenly and uniformly coated on one surface of a copper foil. Then, it is dried at 110°C to obtain a negative electrode sheet with a single-sided coating of negative electrode active material layer. When preparing a double-sided coated negative electrode sheet, the above steps are repeated on the other surface of the negative electrode sheet to obtain a negative electrode sheet with a double-sided coating of negative electrode active material layer. Then, the single-sided negative electrode active material layer is cold-pressed to a thickness of 105 μm, cut, and negative electrode tabs are welded to the empty foil area at the head in the length direction of the copper foil. The material of the negative electrode tabs is nickel.

[0131] (2) Preparation of the positive electrode sheet: Lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97.5:1.0:1.5. N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75 wt%, and the mixture was stirred evenly. The slurry was uniformly coated on one surface of an aluminum foil and then dried at 90°C to obtain a positive electrode sheet with a single-sided coating of the positive active material layer. When preparing a double-sided coated positive electrode sheet, the above coating steps were repeated on the other surface of the aluminum foil. The single-sided positive active material layer was then cold-pressed to a thickness of 95 μm, slit, and positive electrode tabs were welded to the empty foil area at the head of the aluminum foil along its length. The material of the positive electrode tabs was aluminum.

[0132] (3) Preparation of electrolyte: In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are first mixed in a mass ratio of EC:EMC:DEC = 30:50:20 to form a basic organic solvent. Then, lithium salt lithium hexafluorophosphate (LiPF6) is added to the basic organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0133] (4) Preparation of the isolation membrane: A 7-micron thick porous polyethylene polymer film was used as the isolation membrane.

[0134] (5) Electrode assembly fabrication: The unfolded negative and positive electrode sheets are die-cut or laser-cut to form straight and curved sections on the side of the negative electrode sheet along the length of the electrode assembly, and straight and curved sections on the side of the positive electrode sheet along the length of the electrode assembly. The negative electrode sheet, separator, and positive electrode sheet are then stacked and wound together. The straight sections of the negative electrode sheet overlap to form the first side, and the curved sections of the negative electrode sheet overlap to form the first arc. The straight sections of the positive electrode sheet overlap but do not exceed the first side, and the curved sections of the positive electrode sheet overlap to form the third arc.

[0135] (6) Electrode assembly assembly: Place the punched aluminum-plastic film in the assembly fixture with the punched surface facing up, place the electrode assembly in the punch, and apply external force to press it tight. Then cover the electrode assembly with another punched aluminum-plastic film with the punched surface facing down, and heat seal the two aluminum-plastic films around their perimeter by hot pressing to obtain the assembled electrode assembly.

[0136] (7) Electrolyte injection and encapsulation: Electrolyte is injected into the assembled electrode assembly, and the battery cell is obtained through vacuum encapsulation, standing, hot pressing, shaping and other processes.

[0137] Comparative Example 1: The corner of the electrode assembly does not have a first arc. It should be noted that, except for the structural difference in the corner of the electrode assembly, all other parameters in Comparative Example 1 are the same as those in Example 1.

[0138] Comparative Example 2: R2 = R1. It should be noted that, except for the different structure of the corner of the electrode assembly, the other parameters of Comparative Example 1 are the same as those of Example 1.

[0139] Comparative Example 3: R2 > R1. It should be noted that, except for the different structure of the corner of the electrode assembly, the other parameters of Comparative Example 1 are the same as those of Example 1.

[0140] Comparative Example 4: The corner of the electrode assembly does not have a first arc. It should be noted that, except for the structural difference in the corner of the electrode assembly, all other parameters of Comparative Example 1 are the same as those of Example 9.

[0141] Comparative Example 5: R2 = R1. It should be noted that, except for the different structure of the corner of the electrode assembly, the other parameters of Comparative Example 1 are the same as those of Example 9.

[0142] Comparative Example 6: R2 > R1. It should be noted that, except for the different structure of the corner of the electrode assembly, the other parameters of Comparative Example 1 are the same as those of Example 9.

[0143] Table 1

[0144] (The first and second arcs in Examples 1-6 are convex arcs. All parameters in Comparative Examples 1-3 and Examples 2-6 are the same as in Example 1, except for those listed in Table 1.)

[0145]

[0146] As can be seen from Comparative Examples 1-3 and Example 1, when the first arc and the second arc are both convex arcs, by limiting R2 < R1, the risk of cell deformation or damage caused by the corner of the packaging bag squeezing the electrode assembly can be reduced, the safety performance of the cell can be improved, and the energy density of the cell can be increased.

[0147] As can be seen from Examples 1-5, by limiting R2 to 3mm, the energy density of the battery cell can be improved. It should be noted that when R2 is too small (less than 1mm), stress concentration is likely to occur in the second arc, affecting the structural strength of the packaging bag and making the processing of the packaging bag difficult.

[0148] As can be seen from Examples 1 and 6, by limiting R2 2 <R1 2 <L×d1 / (4-π) can improve the energy density of the battery cell.

[0149] Table 2

[0150] (The first and second arcs in Examples 7-12 are concave arcs. All parameters in Comparative Examples 4-6 and Examples 8-12 are the same as in Example 7, except for those listed in Table 2.)

[0151]

[0152] As can be seen from Comparative Examples 4-6 and Example 7, when the first arc and the second arc are concave arcs respectively, by limiting R2 < R1, the risk of cell deformation or damage caused by the corner of the packaging bag squeezing the electrode assembly can be reduced, the safety performance of the cell can be improved, and the energy density of the cell can be increased.

[0153] As shown in Examples 7-11, by limiting R2 to 3mm, the energy density of the battery cell can be improved. It should be noted that when R2 is too small (less than 1mm), stress concentration is likely to occur in the second arc, affecting the structural strength of the packaging bag and making the processing of the packaging bag difficult.

[0154] As can be seen from Examples 7 and 12, by limiting R2 2 <R1 2 <L×d1 / π, which can improve the energy density of the battery cell.

[0155] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be covered within the scope of this application.

Claims

1. A battery cell, characterized in that, The battery cell includes: an electrode assembly, wherein at least one corner of the electrode assembly is provided with a first arc, and the radius of the first arc is R1 when viewed along a first direction; and a packaging bag, wherein the packaging bag includes a main body, the electrode assembly is disposed within the main body, and a second arc is provided at a corner of the main body adjacent to the first arc, the second arc being spaced apart from the first arc, and the radius of the second arc is R2 when viewed along the first direction, where R2 < R1; the first direction is the thickness direction of the battery cell.

2. The battery cell as described in claim 1, characterized in that, 1mm≤R2≤3mm.

3. The battery cell as described in claim 1 or 2, characterized in that, The electrode assembly includes a negative electrode, a positive electrode, and a separator. The negative electrode and the positive electrode are alternately arranged along the first direction, and the separator is disposed between the negative electrode and the positive electrode. Along the first direction, the projection of the positive electrode is located within the projection of the negative electrode, and the first arc is disposed on the negative electrode.

4. The battery cell as described in claim 3, characterized in that, The positive electrode plate has a third arc at the corner adjacent to the first arc. When viewed along the first direction, the radius of the third arc is R3, where R2 < R3 < R1.

5. The battery cell according to any one of claims 1 to 4, characterized in that, Viewed along the first direction, the electrode assembly includes two first side surfaces arranged opposite each other along the second direction, and two second side surfaces arranged opposite each other along the third direction. The first side surfaces and the second side surfaces are connected by the first arc. The first direction, the second direction and the third direction are perpendicular to each other. Viewed along the first direction, the main body includes two first walls arranged opposite each other along the second direction, and two second walls arranged opposite each other along the third direction. The first walls and the second walls are connected by a second arc. The first walls and their corresponding first side surfaces are arranged along the second direction, and the second walls and their corresponding second side surfaces are arranged along the third direction.

6. The battery cell as described in claim 5, characterized in that, Viewed along the first direction, the center of the first arc is located on the electrode assembly, and the center of the second arc is located on the side of the main body facing the electrode assembly.

7. The battery cell as described in claim 6, characterized in that, The angle between the line connecting the first arc and its center is 90°, and the angle between the line connecting the second arc and its center is also 90°. Along the second direction, the distance between the first wall and the corresponding first side surface is d1, and along the third direction, the distance between the two second side surfaces is L. R1, R2, d1, and L satisfy the following relationship: R2 2 <R1 2 <L×d1 / (4-π).

8. The battery cell as described in claim 5, characterized in that, Viewed along the first direction, the center of the first arc is located outside the electrode assembly, and the center of the second arc is located on the side of the main body away from the electrode assembly.

9. The battery cell as described in claim 8, characterized in that, The angle between the line connecting the first arc and its center is 90°, and the angle between the line connecting the second arc and its center is also 90°. Along the second direction, the distance between the first wall and the corresponding first side surface is d1, and along the third direction, the distance between the two second side surfaces is L. R1, R2, d1, and L satisfy the following relationship: R2 2 <R1 2 <L×d1 / π.

10. The battery cell as described in claim 3 or 4, characterized in that, The electrode assembly has a stacked structure or a wound structure.

11. The battery cell according to any one of claims 1 to 10, characterized in that, Along the first direction, the thickness of the battery cell is H, where H ≤ 3.5 mm.

12. A terminal device, characterized in that, The terminal device includes a battery cell as described in any one of claims 1 to 11.

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